Unreachable Code Error in Java

The Unreachable statements refers to statements that won’t get executed during the execution of the program are called Unreachable Statements. These statements might be unreachable because of the following reasons:

  • Have a return statement before them
  • Have an infinite loop before them
  • Any statements after throwing exception in a try block

Scenarios where this error can occur:

  1. Have a return statement before them: When a return statement gets executed, then that function execution gets stopped right there. Therefore any statement after that wont get executed. This results in unreachable code error.

    Example:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    class GFG {
        public static void main(String args[])
        {
      
            System.out.println("I will get printed");
      
            return;
      
            // it will never run and gives error
            // as unreachable code.
            System.out.println("I want to get printed");
        }
    }

    chevron_right

    
    

    Compile Errors:

    prog.java:11: error: unreachable statement
    System.out.println(“I want to get printed”);
    ^
    1 error



  2. Have an infinite loop before them: Suppose inside “if” statement if you write statements after break statement, then the statements which are written below “break” keyword will never execute because if the condition is false, then the loop will never execute. And if the condition is true, then due to “break” it will never execute, since “break” takes the flow of execution outside the “if” statement.

    Example:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    class GFG {
        public static void main(String args[])
        {
            int a = 2;
            for (;;) {
      
                if (a == 2) {
      
                    break;
      
                    // it will never execute, so
                    // same error will be there.
                    System.out.println("I want to get printed");
                }
            }
        }
    }

    chevron_right

    
    

    Compile Errors:

    prog.java:13: error: unreachable statement
    System.out.println(“I want to get printed”);
    ^
    1 error

  3. Any statement after throwing an exception: If we add any statements in a try-catch block after throwing an exception, those statements are unreachable because there is an exceptional event and execution jumps to catch block or finally block. The lines immediately after the throw is not executed.

    Example:

    filter_none

    edit
    close

    play_arrow

    link
    brightness_4
    code

    class GFG {
        public static void main(String args[]) {
      
            try {
                throw new Exception("Custom Exception");
                //Unreachable code
                System.out.println("Hello");
            } catch (Exception exception) {
                exception.printStackTrace();
            }
      
        }
    }

    chevron_right

    
    

    Compile Errors:

    prog.java:7: error: unreachable statement
    System.out.println(“Hello”);
    ^
    1 error

Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.




My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : smithasm7